In this example we have a single supplier that can ship us 100 parts per week.
We need to buy material to meet 3 sales orders from him.

The supplier is also shutting down for summer holidays during July.

The material purchases for the 1st sales order of quantity 370 are
distributed over 4 weeks.

The material purchases for the 2nd sales order of quantity 40 take the remaining
supplier capacity in week 4, and part of week 5. Note that for every purchase
of product Y we consume 2 units from the supplier capacity (ie the supplier can
only provide us 50 units/week of this item.

The material purchases for the 3rd sales order are placed in week 5.

The purchase orders for the 4th sales order due on August 2nd are adjusted
to take this into account. We place the purchase order already at the end
of June.